Friday, August 5, 2011

THE NATIONAL WEATHER SERVICE IN GREENVILLE-SPARTANBURG HAS ISSUED A
* FLOOD WARNING FOR RAPID RIVER RISES IN...
CENTRAL MECKLENBURG COUNTY IN THE PIEDMONT OF NORTH CAROLINA...
SOUTHWESTERN CABARRUS COUNTY IN THE PIEDMONT OF NORTH CAROLINA...
* UNTIL 630 PM EDT
* AT 319 PM EDT...EMERGENCY MANAGEMENT REPORTED FLOODING ACROSS THE
WARNED AREA. OVER 6 INCHES OF RAIN FELL OVER PARTS OF THE WARNED
AREA DURING THE PAST 6 HOURS.
* SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE...CENTER CITY
CHARLOTTE...UNC CHARLOTTE...CHARLOTTE MOTOR SPEEDWAY...EASTLAND
MALL...HARRISBURG...I-77 AT I-85...MINT HILL...PAW CREEK AND
SOUTHPARK MALL.
CREEKS SUCH AS STEWART...LITTLE SUGAR...SUGAR...BRIAR...MCMULLEN AND
BACK CREEK ARE ABOVE FLOOD STAGE AND CONTINUE ABOVE FLOOD STAGE FOR
SEVERAL MORE HOURS.
THIS AREAL FLOOD WARNING WILL REPLACE FLASH FLOOD WARNINGS 18 AND 19.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
EXCESSIVE RUNOFF FROM HEAVY RAINFALL WILL CAUSE FLOODING OF SMALL
CREEKS AND STREAMS...HIGHWAYS AND UNDERPASSES. ADDITIONALLY...
COUNTRY ROADS AND FARMLANDS ALONG THE BANKS OF CREEKS...STREAMS AND
OTHER LOW LYING AREAS ARE SUBJECT TO FLOODING.

Discussion... Slight risk of severe weather from North Dakota into West South Dakota, back through NE Wyoming and East Montana. Slight risk also exists in North Mississippi. Elevated threat of wind will exist in the North Dakota region, with a damaging wind event expected.
As of 1:00 PM/ 18Z... 12Z GFS model indicating a hole of no instability existing in North Mississippi, also where a very strong cap over the atmosphere will exist, preventing storms from developing. While a watch is possible for that area, I anticipate that, in the event some storms develop, they will have only some downdraft (thunderstorm cooled winds) instability to work with. 12Z GFS does indicate some potentially strong storms are to break that cap and introduce some severe weather into the area. There is potential for heavy rain, with precipitable water (PWAT) values exceeding 2.5 inches. This means that if all the air in the atmosphere were condensed, there would be 2.5 inches of water in that column of space.
For the Dakotas, instability will remain not too impressive, with readings coming out at 1000-1750 j/kg. However SE North Dakota is expected to break the 2000 j/kg mark for instability, and that could be the strong point of the storms tonight. PWAT values will exceed 1 inch, and could flirt with 1.5 inches in some areas. SFC (Surface) winds will be converging along a front, so there is tornado potential to the north and south of the front.

Synopsis:ENSO-neutral is expected to continue into the Northern Hemisphere fall 2011, with ENSO-neutral or La Niña equally likely thereafter.

During July 2011, ENSO-neutral was reflected in the overall pattern of small sea surface temperature (SST) anomalies across the equatorial Pacific Ocean (Fig. 1). All of the latest weekly Niño index values were generally near average (Fig. 2), ranging from –0.2oC (Niño-3.4) to 0.5oC (Niño-1+2). However, the subsurface oceanic heat content anomaly (average temperature anomalies in the upper 300m of the ocean, Fig. 3) continued to weaken and is currently near zero, which reflects the strengthening of the below-average temperatures at depth in the east-central Pacific Ocean (Fig. 4). The atmospheric circulation anomalies were more variable during the past month, but the monthly means still reflect aspects of La Niña. For example, convection continued to be enhanced over eastern Indonesia and Papua New Guinea, and generally suppressed over the central equatorial Pacific, mainly south of the equator (Fig. 5). Also, anomalous low-level easterly and upper-level westerly winds persisted over the central tropical Pacific. Thus, while tropical Pacific oceanic anomalies indicate ENSO-neutral, the atmospheric patterns continue to reflect La Niña-like conditions.

The majority of ENSO models, and all multi-model average forecasts (indicated by thicker lines, Fig. 6), indicate ENSO-neutral will continue into the Northern Hemisphere fall 2011 (three-month average in the Niño-3.4 index between –0.5oC and +0.5oC). Beyond the early fall, the forecasts are less certain with half of the models persisting ENSO-neutral conditions continuously through early 2012. Along with a few other models, the latest runs from the NCEP Climate Forecast System (CFS) models predict La Niña to re-develop during the fall (Fig. 7). This forecast is also supported by the ongoing La Niña-like tropical atmosphere, subsurface temperature trends, and the historical tendency for significant wintertime La Niña episodes to be followed by relatively weaker La Niña episodes the following winter. Therefore, ENSO-neutral is expected to continue into the Northern Hemisphere fall 2011, with ENSO-neutral or La Niña equally likely thereafter.

This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA's National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts for the evolution of El Niño/La Niña are updated monthly in the Forecast Forum section of CPC's Climate Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 8 September 2011. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message to: ncep.list.enso-update@noaa.gov.

NOAA's Atlantic hurricane season update calls for increase in named storms

Forecasters have higher confidence for an active season

NOAA issued its updated 2011 Atlantic hurricane season outlook today raising the number of expected named storms from its pre-season outlook issued in May. Forecasters also increased their confidence that 2011 will be an active Atlantic hurricane season. NOAA’s Climate Prediction Center, a division of theNational Weather Service, updates its Atlantic hurricane season outlook every August.

“The atmosphere and Atlantic Ocean are primed for high hurricane activity during August through October,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster at the Climate Prediction Center. “Storms through October will form more frequently and become more intense than we’ve seen so far this season.”

Key climate factors predicted in May continue to support an active season. These include: the tropical multi-decadal signal, which since 1995 has brought favorable ocean and atmospheric conditions, leading to more active seasons; exceptionally warm Atlantic Ocean temperatures (the third warmest on record); and the possible redevelopment of La Niña. Reduced vertical wind shear and lower air pressure across the tropical Atlantic also favor an active season.

Based on these conditions and on climate model forecasts, the confidence for an above-normal season has increased from 65 percent in May to 85 percent. Also, the expected number of named storms has increased from 12-18 in May to 14-19, and the expected number of hurricanes has increased from 6-10 in May to 7-10.

Across the entire Atlantic Basin for the whole season – June 1 to November 30 – NOAA’s updated seasonal outlook projects, with a 70 percent probability, a total of:

14 to 19 named storms (top winds of 39 mph or higher), including:

7 to 10 hurricanes (top winds of 74 mph or higher), of which:

3 to 5 could be major hurricanes (Category 3, 4 or 5; winds of at least 111 mph)

These ranges are indicative of an active season, and extend well above the long-term seasonal averages of 11 named storms, six hurricanes and two major hurricanes.

The Atlantic basin has already produced five tropical storms this season: Arlene, Bret, Cindy, Don and Emily. All eyes this week are on Emily, which continues to develop and move towards the United States.

The last hurricane to make landfall in the United States was Ike in 2008. Last year saw above-normal hurricane activity, but none made landfall in the United States. August through October are peak months of the Atlantic hurricane season, and FEMA urges people not to be lured into a false sense of security by the lack of hurricanes so far this year.

"It is still early in this hurricane season and we know it can take only one storm to devastate communities and families," said FEMA Deputy Administrator Rich Serino. "Many disasters come without warning, but that’s not the case with hurricanes. This is hurricane season, if you haven't already, now is the time to take a few simple steps to get you and your family prepared. Anyone can visit www.ready.gov to learn more."

Be prepared for the hurricane season with important information available online at hurricanes.gov/prepare and at FEMA’s ready.gov.

NOAA’s mission is to understand and predict changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. Join us onFacebook, Twitter and our other social media channels.

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